Reply
 
Thread Tools Display Modes
 
Old 04-15-2017, 11:16 AM   #1
Mini-Skoolie
 
Join Date: Sep 2016
Location: Hesperia, CA
Posts: 22
Year: 1982
Coachwork: Carpenter
Chassis: Ford B600
Engine: 8.2l Detroit diesel
Rated Cap: 28
Connecting inverter to battery bank

Sorry, but one more off the wall electric question:

3 batteries in parallel. Does the inverter need to be wired to all 3, i.e 3 + and 3- wires coming together then to the inverter, like the main wiring does on the bus? Or can it be wired to just one battery, and be drawing from all 3, since they are already wired together?
DAVEHOLMAN is offline   Reply With Quote
Old 04-15-2017, 12:08 PM   #2
Bus Geek
 
Robin97396's Avatar
 
Join Date: Feb 2016
Location: Willamina, Oregon
Posts: 6,409
Coachwork: 97 Bluebird TC1000 5.9
In a parallel circuit you connect the positive and negative leads to the inverter the same as if you were connecting positive and negative from a single battery.
__________________
Robin
Nobody's Business
Robin97396 is offline   Reply With Quote
Old 04-15-2017, 03:38 PM   #3
Bus Crazy
 
Join Date: Feb 2012
Location: Salt Lake City Utah
Posts: 1,518
Year: 2000
Chassis: Blue Bird
Engine: ISC 8.3
We just recently had an interesting conversation on the difference made by the arrangement of the interconnects in a battery bank. It was focused on banks of 4 or 8 batteries, but you may still find it interesting. It's there.

For a number of batteries that isn't a power of 2 (such as your 3) the star configuration in which matched cables go from each battery post back to a single terminal, and from there to the loads (such as an inverter) would be ideal.
family wagon is offline   Reply With Quote
Old 04-15-2017, 03:40 PM   #4
Bus Crazy
 
joeblack5's Avatar
 
Join Date: Dec 2015
Location: pa
Posts: 1,320
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford e350 2 mercedes
Engine: 7.3 powerstroke & MBE906
Assuming your batteries are the same then you would like to draw an equal current from each battery. A good way to do that would be as you described taking three plus wires and three minus wires. The wires should have about the same length and be the same gauge. If you take that approach you technically need also three fuses. One in each line and rated 1/3 or a little larger then the fuse normally recommended for your size inverter.

Because of the pain of three fuses and other wiring hassles associated with three lines most people just parallel the batteries at the terminal and then get one big wire to the inverter.

Later j
joeblack5 is offline   Reply With Quote
Old 04-15-2017, 04:16 PM   #5
Mini-Skoolie
 
Join Date: Sep 2016
Location: Hesperia, CA
Posts: 22
Year: 1982
Coachwork: Carpenter
Chassis: Ford B600
Engine: 8.2l Detroit diesel
Rated Cap: 28
Quote:
Originally Posted by joeblack5 View Post
Assuming your batteries are the same then you would like to draw an equal current from each battery. A good way to do that would be as you described taking three plus wires and three minus wires. The wires should have about the same length and be the same gauge. If you take that approach you technically need also three fuses. One in each line and rated 1/3 or a little larger then the fuse normally recommended for your size inverter.

Because of the pain of three fuses and other wiring hassles associated with three lines most people just parallel the batteries at the terminal and then get one big wire to the inverter.

Later j

Yeah...that's how they go up to the engine compartment. I suppose i could splice in to the existing 0 gauge, but I'm a little leery of messing that up and not only killing an inverter, but the starter and alternator, etc, as well 😆
DAVEHOLMAN is offline   Reply With Quote
Old 04-15-2017, 04:20 PM   #6
Mini-Skoolie
 
Join Date: Sep 2016
Location: Hesperia, CA
Posts: 22
Year: 1982
Coachwork: Carpenter
Chassis: Ford B600
Engine: 8.2l Detroit diesel
Rated Cap: 28
RELATED: As long as the engine is running, I'm not actually drawing down the batteries, right? My 130 amp/hr alternator should power everything I'm hooking up and still have power left to keep the batteries topped up.
DAVEHOLMAN is offline   Reply With Quote
Old 04-16-2017, 01:53 PM   #7
Bus Nut
 
tobeamiss's Avatar
 
Join Date: Oct 2016
Location: NY
Posts: 729
Year: 2002
Coachwork: International
Engine: dt466
Rated Cap: 65C-43A
Quote:
Originally Posted by DAVEHOLMAN View Post
RELATED: As long as the engine is running, I'm not actually drawing down the batteries, right? My 130 amp/hr alternator should power everything I'm hooking up and still have power left to keep the batteries topped up.
That's something I'd like to know as well. I'm gathering all of this information for when I'm ready. I won't be doing the work myself because I'm clueless but i will be supervising.

Sent from my SM-T350 using Tapatalk
__________________
oh yes she did!
http://www.skoolie.net/forums/f11/to...-it-16557.html
tobeamiss is offline   Reply With Quote
Old 04-16-2017, 11:08 PM   #8
Bus Crazy
 
Join Date: Feb 2012
Location: Salt Lake City Utah
Posts: 1,518
Year: 2000
Chassis: Blue Bird
Engine: ISC 8.3
Well that's a great big "It Depends."
  • how much power is being drawn through the inverter? That alternator might have a nominal output of 13.8 volts * 130 amps = 1794 watts, but...
  • how fast is the alternator spinning? Alternators frequently don't have a flat output power vs input RPM graph. Many produce substantially less than their nameplate nominal rating at idle.
  • how much does the output voltage of the inverter sag when the inverter load is applied? Or, more importantly, how much does the voltage at the battery terminals sag? Lead batteries won't take a charge at all until voltage is above 12.9 volts. They'll just barely charge at that voltage though; often charge voltage is up to 14.1 volts in order to hurry things along. If the voltage at the battery while alternator and inverter are running is low in this range then the battery will be recharging slowly; if the voltage drops much under 12.9 then it'll be discharging despite the alternator running. Depending on the regulation of the alternator, its input speed, resistances in the circuit, etc this could happen well before 130 amps of load is applied.
Don't take this as "it can't be done;" I don't mean it that way at all. I only mean to show at a high level what are some of the factors so that a person can make estimates about whether their situation has a high likelihood of working well, and give ideas about how that person could then build it and do experiments to determine how well their specific setup is meeting their needs.
family wagon is offline   Reply With Quote
Old 04-17-2017, 08:14 AM   #9
Mini-Skoolie
 
Join Date: Sep 2016
Location: Hesperia, CA
Posts: 22
Year: 1982
Coachwork: Carpenter
Chassis: Ford B600
Engine: 8.2l Detroit diesel
Rated Cap: 28
Food for thought. Thanks
DAVEHOLMAN is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 04:15 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.